Musical instrument string tensioning means



1942- G. PROELSDORFER 2,304,597

MUSICAL INSTRUMENT STRING TENSIONING MEANS Filed Aug. 15, 1942 WWW/1INVENTOR. wzi j'i 'oggiozfer,

Patented Dec. 8, 1942 zse sw UNITED STATES PATENT OFFICE MUSICALINSTRUMENT STRING TENSION- ING MEANS 3 Claims.

This invention relates to improvements in means for tensioning stringsof stringed musical instruments, such e. g. as violins, cellos, guitarsand the like; and the invention has reference, more particularly, to animproved tensioning device for application to .a tail-piece of astringed musical instrument to which the anchored end of a string may beattached, whereby, upon manipulation of the tensioning device a veryaccurate final tuning of the attached string may be attained.

Tensioning devices of the general kind involved in the instantinvention, as heretofore known, have comprised a pivoted bell-cranklever fulcrumed on a bracket plate which is affixed to the 1 instrumenttail-piece, the tail end of a string being attached to the upstandingarm of said bell-crank lever, and manipulatable means being provided forrocking the bell-crank lever so as to apply a tensioning pull upon thestring,

attached thereto. In some forms of tensioning devices of this kind, thebell-crank lever is fulcrumed on a pivot pin carried by thebracketplate, such construction requiring very accurate drilling of boththe bell-crank lever and bracketplate, which involved difficult and timeconsuming operations both as to the drilling and assembling of theseelements :in view of the small size of the parts operated on. Attemptshave heretofore been made to avoid use of a pivot pin, and necessity forthe difiicult drilling and assembling operations such use involved; andto this end it has been proposed to slot the bracket plate to receive aflattened fulcruming section with which the bell-crank lever wasprovided, the bracket plate being slit longitudinally through itsslotted part, whereby the same could be expanded for the insertion ofthe said flattened fulcruming section, and then squeezed together again,so as to embrace the latter. In practice, however, this solution doesnot seem to be altogether satisfactory, largely for the reason that aclose fit and embrace of the bracket plate about fulcruming section ofthe bell-crank lever is both difiicult to. attain and maintain, with theconsequence that a tendency of the bell-crank lever .to wobble and shiftunder the strain of the string tensioned thereby occurred, with risk ofaltering the string tension and resultant loss of accurate tuning.

Having these faults of previous tensioning de vices in view, it is anobject of the present invention to provide an improved tensioning deviceconstruction, and especially improved means for mounting, fulcruming andassembling the be11- crank lever in connection with the bracket plate,without necessity for use of a pivot pin and involved drillingoperations, and whereby a firm rocking support of the bell-crank leverfree from looseness and tendency to wobble or shift is provided.

Other objects of the present invention, not at this time moreparticularly enumerated, will be understood from the following detaileddescription of the same.

An illustrative embodiment of the present invention is shown in theaccompanying drawing, in which:

Fig. 1 is a fragmentary plan View of a violin, including its tail-piece,and showing a string tensioning device according to this inventionoperatively mounted on the latter; 2 is a longi tudinal sectional view,taken on line 2-2 in Fig. 1, but drawn on a greatly enlarged scale; Fig.3 is a horizontal sectional View, taken on line 33 in Fig. 2; Fig. 4 isa transverse vertical section, taken on line 3-3 in Fig. 2; and Fig. 5is a fragmentary plan view of the bell-crank lever fulcruming endportion of the bracket plate of the device.

Similar characters of reference are employed in the above describedviews, to indicate corresponding parts.

Referring to the drawing, the reference character I0 indicates a portionof the rear end of a violin, to which is attached, in the usual manner,its tail-piece II. Said tail-piece H is provided with the usual key-holeslots [2 ordinarily employed for anchoring the strings of theinstrument.

The novel tensioning device according to this invention comprises abracket plate i3. Upstanding from the rear end portion of said bracketplate I3 is an externally screw-threaded post id. Said post I 4 isprovided at its lower end with an anchoring portion l5 of reduceddiameter, adapted to be inserted through an opening provided through therear end portion of said bracket plate to receive the same, untilstopped by the shoulder it which foots upon the upper surface of saidbracket plate. The free end of said anchoring portion is extended andriveted over, as at ll, against the underside of said bracket plate,thus rigidly securing the post 44 in upstanding relation to said bracketplate.

In applying the bracket plate to the tail-piece II, the post [4 isinserted upwardly through a key-hole slot l2 of the latter, so that thebracket plate abuts the underside of said tail-piece to extendlongitudinally and forwardly therealong.

Said bracket plate is of such length that its forward end portionprojects freely beyond the forward extremity of said tail-piece. Tosecure the bracket plate in such operative assembled relation to thetail-piece, a fastening nut i8 is screwed onto the upper end portion ofthe post, and turned home against the top of the tailpiece with clampingeffect. Preferably the lower end of said nut I8 is provided with aninverted conical portion H] which enters the circular portion of thekey-hole slot I2, thus further stabilizing the bracket plate fromdisplacing shift from its proper assembled relation to said tail-piece.Said post I4 is provided with an internally screwthreaded bore 23 toextend axially therethrough, and threaded through said bore is anadjusting screw 2|, to the upper end of which is affixed a knurled head22 by which the same may be manipulated.

Formed in the freely projecting forward end portion of said bracketplate |3 is a T-shaped slot comprising a transverse slot portion 23 anda longitudinal slot portion 24 extending forwardly therefrom.

The metallic bell-crank lever of the device comprises a substantiallyvertical upper arm 25 and a substantially horizontal lower arm 25.Adjacent to and somewhat above the elbow 21 which connects said arms,the metal of the upper arm is swaged or otherwise worked to form alaterally reduced and flattened fulcrum section 28 having a forwardarcuate edge portion 29 and a rearward arcuate edge portion 39, thecurvature of which form arcs of a common circle described from thecenter of said fulcrum section 28. The thickness width of said fulcrumsection 28 is sized to correspond to the width of the longitudinal slotportion 24 of the T-shaped slot with which the bracket plate I3 isprovided. Said upper arm 25 of the bell-crank lever is preferably ofcircular cross sectional shape, and the free end portion of said upperarm 25 is formed to provide a shallow hook-like formation 3|, to whichthe tail end of the instrument string S to be tensioned is suitablyattached or coupled. The space provided at the intersection of thetransverse and longitudinal slot portions 23 and 24 of the T-shaped slotprovided in the bracket plate I3 is large enough to permit of end Wiseinsertion of the upper arm 25 of the bell-crank lever therethrough. Inassembling the bellcrank lever with the bracket plate, said upper arm 25of the former is inserted upwardly through the T-shaped slot of thelatter, until the flattened fulcrum section 28 is opposed to thelongitudinal. slot portion 24, whereupon said fulcrum section 28 ispushed forward into said longitudinal slot portion 24 until its forwardarcuate edge portion 29 bears against the forward closed end 32 of saidslot portion. The sides of said longitudinal slot portion 24 closely hugthe opposite faces of the inserted fulcrum 28, so that the latter may beclosely embraced by and yet slidingly engage said slot portion sideswithout permitting lateral looseness or play in the movement of thebell-crank lever as thus supported. The forward arcuate edge portion 29provides a fulcrum point which abuts and moves on the closed end wall 32of said longitudinal slot portion 2 3. In order to retain such movingand fulcruming contact of said forward arcuate edge portion 29 with theslot end wall 32, a cylindrical locking pin or key 33 is provided. Thispin or key 33 is forced into the transverse slot sized to tightly fitwithin the same so as to be wedged thereinto, and thus firmly andstrongly held against accidental displacement. Said pin or key presentsthe forward side of its cylindrical surface in contact with and tangentto the rearward arcuate portion 30 of the fulcrum section 28, and thusbears upon the latter throughout the scope of the rocking movement ofthe bellcrank lever so as to guide the movements of said fulcrum section28 while nevertheless preventing relative separation of the fulcrumingforward arcuate edge portion 29 and the slot end wall 32 upon which itbears.

By virtue of the above described fulcruming construction, the bell-cranklever although free to swing on the bracket plate is nevertheless firmlyand securely embraced and held against all looseness and play betweenthe same and the supporting bracket plate, and consequently no wobblingor accidental shift is permitted which, if allowed to occur, might relaxor otherwise disturb the tension which has been applied to the attachedstring by manipulative adjustment of the bell-crank lever.

The horizontal lower arm 26 of the bell-crank lever extends rearwardlybelow the underside of the bracket plate |3, so that its free endportion, which may be suitably provided with a flattened and preferablysomewhat concave upper bearing face 34, is opposed to the extremity 35of the adjusting screw 2|.

In manipulating the device, when the adjusting screw 2| is turned downthrough the post |4 its extremity 35 will engage and thrust downwardlyupon the arm 23 of the bell-crank lever, thus rocking the latter on itsfulcruming connection with the bracket plate so as to swing rearwardlythe upper arm 25, thereby stressing the string S longitudinally to adesired adjusted and precise degree of tension.

The novel fulcruming connection provided by this invention assures afirm pivotal support for the bell-crank lever, free from looseness, playor wobbling, and since the integrity of the bracket plate is notinterrupted by slits or other weakening factors, its operative embraceof bell-crank lever undergoes no risk of relaxation and consequentloosening by reason of spreading of parts thereof. Furthermore, theoperations of assembling the bell-crank lever and bracket plate, and thefinal insertion of the locking pin or key 33, are all capable of beingquickly and easily carried out with a minimum of labor.

Having described my invention, I claim:

In a string tensioning means for musical instruments, a bracket-platehaving means at its rear end portion for attaching the same to and forextension from an instrument tail-piece, said bracket-plate having aT-shaped slot formed therein adjacent to its forward end, a stringsupporting bell-crank lever having a flattened fulcrum section boundedby front and rear arcuate edge portions, the curvature of which formarcs of a common circle, said fulcrum section being entered in thelongitudinal portion of said T- shaped slot so as to be closely embracedby the sides of the latter and with one arcuate edge portion thereofbearing on the end wall of said slot portion, a key element imbeddinglywedged into the transverse portion of said T-shaped slot so as to beartangentially upon the other arcuate edge portion of said fulcrumsection, whereby to retain the latter in the pivoting embrace of saidlongitudinal slot portion, and means to rockingly adjust said bell-cranklever to tension the string supported thereby.

2. In a string tensioning device for musical instruments, an adjustablestring anchoring bellcrank lever and a bracket plate to pivotallysupport the same, said bracket plate having a T-shaped slot, saidbell-crank lever having a flattened fulcrum section entered in theembrace of the longitudinal portion of said slot, a key elementimbeddingly wedged in the transverse portion of said slot, and saidfulcrum section having oppositely directed arcuate edge portions, thecurvature of which form arcs of a common circle, one said edge portionbearing on the end wall of the longitudinal portion of said slot, andthe other said edge portion bearing on said key element.

3. In a string tensioning device for musical instruments, an adjustablestring anchoring bellcrank lever and a bracket plate to pivotallysupport the same, said bracket plate having a T- shaped slot, saidbell-crank lever having a flattened fulcrum section entered in theembrace of the longitudinal portion of said slot, a key elementimbeddingly wedged in the transverse portion of said slot, and saidfulcrum section having oppositely directed arcuate edge portions, thecurvature of which form arcs of a common circle, one said edge portionbearing on the end wall of the longitudinal portion of said slot, theother said edge portion bearing on said key element, means to affix saidbracket plate to the tailpiece of a musical instrument, and meanscarried by said bracket plate to rockingly adjust said bell-crank leverto tension the string attached thereto.

GUSTAVE PROELSDORFER.

